MongoDB

The most popular of the NoSQL offerings (according to multiple surveys), MongoDB was designed by the founders of DoubleClick, the web ads-serving company, who wanted a database that could scale out easily. MongoDB employs a document-based model that stores data using BSON — a binary-capable variant of JSON. The database is remarkably easy to install and use. It has built-in support for sharding and uses a master/slave replication scheme with automatic failover. Unlike some of the key-value stores discussed here, MongoDB allows you to use secondary indexes, and retrieve and sort items on any key.

As explained in our tutorial, to store large data sets, MongoDB requires the addition of GridFS; other entries, such as arrays of data items, are limited to 16MB each.

While MongoDB is open source, high-end tools from 10gen require a commercial license.

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